HSL to RGB color conversion

Question

I am looking for a JavaScript / PHP algorithm to convert between HSL color to RGB.

It seems to me that HSL is not very widely used so I am not having much luck search

Answer 1

I got this from Brandon Mathis' HSL Picker source code.

It was originally written in CoffeeScript. I converted it to JavaScript using an online converter, and took out the mechanism to verify the user input was a valid RGB value. This answer worked for my usecase, as the most up-voted answer on this post I found to not produce a valid HSL value.

Note that it returns an hsla value, with a representing opacity/transparency. 0 is completely transparent, and 1 fully opaque.

function rgbToHsl(rgb) {
  var a, add, b, diff, g, h, hue, l, lum, max, min, r, s, sat;
  r = parseFloat(rgb[0]) / 255;
  g = parseFloat(rgb[1]) / 255;
  b = parseFloat(rgb[2]) / 255;
  max = Math.max(r, g, b);
  min = Math.min(r, g, b);
  diff = max - min;
  add = max + min;
  hue = min === max ? 0 : r === max ? ((60 * (g - b) / diff) + 360) % 360 : g === max ? (60 * (b - r) / diff) + 120 : (60 * (r - g) / diff) + 240;
  lum = 0.5 * add;
  sat = lum === 0 ? 0 : lum === 1 ? 1 : lum <= 0.5 ? diff / add : diff / (2 - add);
  h = Math.round(hue);
  s = Math.round(sat * 100);
  l = Math.round(lum * 100);
  a = parseFloat(rgb[3]) || 1;
  return [h, s, l, a];
}